Four. Commonly made from heat-resistant nylon or polyester, the colorful, usually 80-foot-tall " balloon" part — called the envelope — is laid out on the ground preflight to be partially filled with cold air.
四、通常由耐热尼龙或聚酯制成,颜色鲜艳,通常有 80 英尺高部分被称为“球囊”,它在飞行前被放置在地面,使其部分充满冷空气。